A new methodology is proposed for the synthesis of polycyclic alkaloids. The cornerstone of this approach is to dearomatize a pyrrole, both selectively and reversibly through eta-2-coordination to osmium(II), and use this adduct as a synthon for the assembly of polycyclic alkaloids. Coordination of the heterocycles serves to 1) enhance the reactivity of the ligand, 2) to stabilize reactive intermediates (e.g. 2H or 3H- pyrrolium species), 3) to protect the site of coordination, and 4) to direct the stereochemistry of various chemical transformations.